When mobile stations including mobile phones in the related art receive a call addressed thereto from another mobile station, the mobile stations transmit and receive various messages needed for establishing lines and handling incoming and outgoing calls, to and from a base station and a higher-level device thereof. In particular, in long-term evolution (LTE), which is a wireless communication system that is becoming increasingly common in recent years, when power is turned on, a mobile station establishes lines with a base station and a mobility management entity (MME) or a serving-gateway (S-GW) on a core network by an attaching process so as to be located in a communication area. This process allows the mobile station to receive calls addressed to the mobile station from another mobile station via the base station and the core network. Thereafter, for example, when the power of the mobile station is turned off, the mobile station requests the MME to delete the location information thereof (detaching process) via the base station. Upon receiving the request, the MME deletes the location information of the mobile station to complete the detaching process.
Japanese Laid-open Patent Publication No. 2009-290578, No. 2010-199715, No. 2010-68184, No. 2011-188040, No. 2010-157918 are examples of related art.